Load Partitioning Research Articles

Load partition and microstructural evolution during in situ hot deformation of Ti–6Al–6V–2Sn alloys

Two Ti–6Al–6V–2Sn alloys, with globular and lamellar microstructures, are deformed at 750°C during tensile and compression tests. The lamellar microstructure shows softening and higher peak stress values than the globular microstructure as a consequence of the Hall–Petch effect. In-situ high energy synchrotron diffraction experiments allow characterization of the load partition between α- and β-phases, plastic deformation mechanisms and texture evolution. The α-phase deforms mainly by rotation while the β-phase deforms by misorientation formation, acting merely as load transfer agent. The Taylor factor evolution of the α-phase and the annihilation of dislocations are analyzed qualitatively and quantitatively. The Taylor factor is connected to both the softening observed in the alloy with the lamellar microstructure and the texture development.

Development of a cloud-based factory simulation system for enabling ubiquitous factory simulation

This study investigated several problems related to the implementation of cloud-based factory simulation. First, the differences between cloud-based factory simulation and parallel and distributed factory simulation were discussed. Individually managed, resource heterogeneity, uneven load partitioning, and potential business opportunities were found to be the novel characteristics that discriminate cloud-based factory simulation from parallel and distributed factory simulation. The problems in existing cloud-based factory simulation systems are discussed. An experimental cloud-based factory simulation system was developed and used for simulating a mobile lift table factory. We investigated problems related to the implementation of cloud-based factory simulation.We discussed differences between cloud-based and parallel or distributed simulations.We discussed problems in existing cloud-based factory simulation systems.We developed an experimental cloud-based factory simulation system.

Study of the mechanical behavior of the hydride blister/rim structure in Zircaloy-4 using in-situ synchrotron X-ray diffraction

High-energy synchrotron X-ray diffraction was utilized to study the mechanical response of the f.c.c δ hydride phase, the intermetallic precipitation with hexagonal C14 lave phase and the α-Zr phase in the Zircaloy-4 materials with a hydride rim/blister structure near one surface of the material during in-situ uniaxial tension experiment at 200 °C. The f.c.c δ was the only hydride phase observed in the rim/blister structure. The conventional Rietveld refinement was applied to measure the macro-strain equivalent response of the three phases. Two regions were delineated in the applied load versus lattice strain measurement: a linear elastic strain region and region that exhibited load partitioning. Load partitioning was quantified by von Mises analysis. The three phases were observed to have similar elastic modulus at 200 °C.

Solving a hydrodynamic problem on a method of multipoint search in a distributed computing environment

The method of multipoint search for numerical solution of a hydrodynamic problem is offered. Theproblem of optimization of partition of calculation load between the nodets of the distributedcomputing environment at realization of this method is considered. The use of the offered methodallows to go round local minimums of the target function and optimize the use of computing resources

Unified description of the softening behavior of beta-metastable and alpha+beta titanium alloys during hot deformation

In this work, we propose a unified description of the softening behavior of a β metastable alloy and Ti6Al4V alloy. In the first part we provide sound evidence that the hot deformation of Ti6Al4V of the beta phase above and below the beta transus temperature takes place solely by dynamic recovery at moderate strains, similarly to the behavior of the Ti5Al5Mo5V3Cr1Zr near-beta alloy. This study was possible due to the combination of the fast cooling rates achieved after controlled hot deformation and the reconstruction of the parent beta phase from electron backscattered diffraction measurements of the frozen alpha phase by using an innovative developed algorithm. The dynamic recovery as a common dynamic restoration behavior for Ti6Al4V and Ti5Al5Mo5V3Cr1Zr is described mathematically with a Derby type relationship of the subgrain size and the stress of the beta phase. A rule of mixture allows the determination of the load partition between the two allotropic phases.

Understanding low-cycle fatigue life improvement mechanisms in a pre-twinned magnesium alloy

The mechanisms of fatigue life improvement by pre-twinning process in a commercial rolled magnesium (Mg) alloy have been investigated using real-time in situ neutron diffraction under a continuous-loading condition. It is found that by introducing the excess twinned grains through pre-compression along the rolling direction the fatigue life was enhanced approximately 50%, mainly resulting from the prolonged detwinning process and inhibited dislocation slip during reverse tension. Moreover, after pre-twinning, the reduction of the rapid strain hardening during reverse tension leads to a compressive mean stress value and more symmetric shape of stress–strain hysteresis loop. The pre-twinning has significant impacts on the twinning-detwinning characteristics and deformation modes during cyclic loading and greatly facilitates the twinning-detwinning activities in plastic deformation. The cyclic straining leads to the increase of contribution of tensile twinning deformation in overall plastic deformation in both the as-received and pre-twinned sample. The mechanisms of load partitioning in different groups of grains are closely related to the deformation modes in each deformation stage, while the fatigue cycling has little influence on the load sharing. The pre-twinning process provides an easy and cost-effective route to improve the low-cycle fatigue life through manufacturing and processing, which would advance the wide application of light-weight wrought Mg alloys as structural materials.

On the microstructure and strengthening mechanism in oxide dispersion-strengthened 316 steel: A coordinated electron microscopy, atom probe tomography and in situ synchrotron tensile investigation

An oxide dispersion-strengthened (ODS) 316 steel was developed to simultaneously provide the advantages of ODS steels in mechanical strength and radiation tolerance as well as the excellence of austenitic steels in creep performance and corrosion resistance. The precipitate phases within the austenite matrix were identified by the combined techniques of atom probe tomography (APT), scanning transmission electron microscopy equipped with electron dispersive X-ray spectroscopy (STEM-EDS), and synchrotron wide-angle and small-angle X-ray scattering (WAXS and SAXS). Coarse TiN, hexagonal YAlO3 and orthorhombic YAlO3 precipitates were found along with fine Y–Ti–O nanoparticles. In situ WAXS experiments were performed at room and elevated temperatures to examine the size effect on the load partitioning phenomenon for TiN, hexagonal YAlO3 and Y2Ti2O7 phases. In addition, the dislocation density evolution throughout the tensile tests was analyzed by the modified Williamson–Hall method and confirmed by transmission electron microscopy (TEM) observations, revealing the difference in plasticity at various temperatures.

Increasing household solar energy penetration through load partitioning based on quality of life: The case study of Nigeria

The inadequate power supply in Nigeria has resulted into the use of diesel/petrol generator by almost every household. The implicating death and health risk recorded has made sustainable alternative sources imperative. Solar energy has been identified as a viable option; however, the greatest challenge is its affordability due to high installation cost. This paper proposes the installation of solar energy system using energy partitioning approach based on scalable level of importance to quality of life. First, household energy utilization is partitioned into different energy sectors, and then the importance of each sector as it affects the basic quality of life of the intending users are determined using structured questionnaire. Using a typical medium income house as a case study, different analyses are performed based on the level of quality of life that can be afforded by the different users. The result reveals that the life cycle cost over a period of 20yr, of solar energy system for level 1 (Lighting only) which has the highest impact on the quality of life of Nigerian is $10,600. The cost of energy is 0.3341$/kWh, the cost of diesel fuel saved 1380$/annum, the break-even point is 7.7yr and the estimated carbon credit is 1095.7kg/yr.

Load partitioning between ferrite/martensite and dispersed nanoparticles of a 9Cr ferritic/martensitic (F/M) ODS steel at high temperatures

In this study, a high-energy synchrotron radiation X-ray technique was used to investigate the tensile deformation processes of a 9Cr-ODS ferritic/martensitic (F/M) steel at different temperatures. Two minor phases within the 9Cr-ODS F/M steel matrix were identified as Y2Ti2O7 and TiN by the high-energy X-ray diffraction, and confirmed by the analysis using energy dispersive X-ray spectroscopy (EDS) of scanning transmission electron microscope (STEM). The lattice strains of the matrix and particles were measured through the entire tensile deformation process. During the tensile tests, the lattice strains of the ferrite/martensite and the particles (TiN and Y2Ti2O7) showed a strong temperature dependence, decreasing with increasing temperature. Analysis of the internal stress at three temperatures showed that the load partitioning between the ferrite/martensite and the particles (TiN and Y2Ti2O7) was initiated during sample yielding and reached to a peak during sample necking. At three studied temperatures, the internal stress of minor phases (Y2Ti2O7 and TiN) was about 2 times that of F/M matrix at yielding position, while the internal stress of Y2Ti2O7 and TiN reached about 4.5–6 times and 3–3.5 times that of the F/M matrix at necking position, respectively. It indicates that the strengthening of the matrix is due to minor phases (Y2Ti2O7 and TiN), especially Y2Ti2O7 particles. Although the internal stresses of all phases decreased with increasing temperature from RT to 600°C, the ratio of internal stresses of each phase at necking position stayed in a stable range (internal stresses of Y2Ti2O7 and TiN were about 4.5–6 times and 3–3.5 times of that of F/M matrix, respectively). The difference between internal stress of the F/M matrix and the applied stress at 600°C is slightly lower than those at RT and 300°C, indicating that the nanoparticles still have good strengthening effect at 600°C.

SmartRank: a smart scheduling tool for mobile cloud computing

Resource scarcity is a major obstacle for many mobile applications, since devices have limited energy power and processing potential. As an example, there are applications that seamlessly augment human cognition and typically require resources that far outstrip mobile hardware's capabilities, such as language translation, speech recognition, and face recognition. A new trend has been explored to tackle this problem, the use of cloud computing. This study presents SmartRank, a scheduling framework to perform load partitioning and offloading for mobile applications using cloud computing to increase performance in terms of response time. We first explore a benchmarking of face recognition application using mobile cloud and confirm its suitability to be used as case study with SmartRank. We have applied the approach to a face recognition process based on two strategies: cloudlet federation and resource ranking through balanced metrics (level of CPU utilization and round-trip time). Second, using a full factorial experimental design we tuned the SmartRank with the most suitable partitioning decision calibrating scheduling parameters. Nevertheless, SmartRank uses an equation that is extensible to include new parameters and make it applicable to other scenarios.

In situ synchrotron tensile investigations on the phase responses within an oxide dispersion-strengthened (ODS) 304 steel

Austenitic oxide dispersion-strengthened (ODS) alloys provide excellent mechanical strength and radiation tolerance along with their intrinsic advantages in corrosion resistance and high temperature creep resistance. This paper reports the in situ synchrotron X-ray diffraction (XRD) tensile test results of ODS 304 stainless steel specimens. The oxygen-enriched nanoparticles were first characterized by both atom probe tomography (APT) and analytic scanning transmission electron microscopy (STEM). Three different types of precipitate phases were recognized, including large scale (around 100nm) TiN, intermediate scale (around 20nm) Y–Al–O, and small scale (<5nm) Y–Ti–O. The lattice responses of different phases within the alloy to the externally applied stress indicate a prominent load partitioning phenomenon. This phenomenon was found to be highly dependent on the size of the precipitates. In addition, deformation-induced martensitic transformation was examined by the modified Williamson–Hall analyses of peak broadening, and was found to be different from that in ordinary 304 stainless steel.

Detection of the Three Gorges Dam influence on the Changjiang (Yangtze River) submerged delta.

While most large river-deltas in the world are facing the risk of subsidence and erosion in the Anthropocene, it is suspected that the Changjiang submerged delta (CSD) could be subjected to the impacts of the world's largest dam, the Three Gorges Dam (TGD). Here we firstly indicate that the CSD went through high accumulation (1958–1978); slight accumulation (1978–1997), slight erosion (1997–2002); and high accumulation (2002–2009), despite the 70% reduction of the sediment load from upstream since the operation of the TGD in 2003. Meanwhile, at the depocenter of the submerged delta, the accumulation maintained a high rate of 10 cm/yr during 1958–2009. This suggests on a longer term, the distal sediment source from the upstream had little effect on the CSD. Within this time frame the changes in the partition of sediment load among the branching channels of the Changjiang Estuary could likely control the shifting of the depocenter of the CSD on a decadal time scale. Episodic extreme floods and storm surges also increased the magnitude of deposition and erosion of the CSD on short-term scales. A re-evaluation of the impacts of TGD on the CSD is urgently needed.

Synchrotron study on load partitioning between ferrite/martensite and nanoparticles of a 9Cr ODS steel

Oxide dispersion strengthened (ODS) steels exhibit exceptional radiation resistance and high-temperature creep strength when compared to traditional ferritic and ferritic/martensitic (F/M) steels. Their excellent mechanical properties result from very fine nanoparticles dispersed within the matrix. In this work, we applied a high-energy synchrotron radiation X-ray to study the deformation process of a 9Cr ODS steel. The load partitioning between the ferrite/martensite and the nanoparticles was observed during sample yielding. During plastic deformation, the nanoparticles experienced a dramatic loading process, and the internal stress on the nanoparticles increased to a maximum value of 3.7GPa, which was much higher than the maximum applied stress (∼986MPa). After necking, the loading capacity of the nanoparticles was significantly decreased due to a debonding of the particles from the matrix, as indicated by a decline in lattice strain/internal stress. Due to the load partitioning, the ferrite/martensite slightly relaxed during early yielding, and slowly strained until failure. This study develops a better understanding of loading behavior for various phases in the ODS F/M steel.

Deformation Behaviour of TRIP Steel Monitored by &lt;i&gt;In Situ&lt;/i&gt; Neutron Diffraction

The paper presents results of in-situ neutron diffraction experiments aimed on monitoring the phase evolution and load distribution in transformation induced plasticity (TRIP) steel when subjected to tensile loading. Tensile deformation behaviour of two TRIP-assisted multiphase steel with slightly different microstructures resulted from different thermo-mechanical treatments applied was investigated by in-situ neutron diffraction. The steel with lower retained austenite volume fraction (fγ=0.04) and higher volume fraction of needle-like bainite in the α-matrix exhibits higher yield stress (sample B, 600MPa) but considerably lower elongation in comparison to the steel with higher austenite volume fraction (fγ=0.08), granular bainite and ferrite matrix (sample A, 500 MPa). The neutron diffraction results showed that the applied tensile load is redistributed at the yielding point in a way that the retained austenite bears a significantly larger load than the α-matrix during the TRIP steel deformation. Steel sample with higher volume fraction of retained austenite and less strong ferrite matrix proved to be a better TRIP steel with respect to strength, ductility and the side effect of the strain induced austenite-martensite transformation. The transforming retained austenite in time of loading provides potential for higher ductility of experimental TRIP steel but at the same time acts as a reinforcement phase during the further plastic deformation.TRIP steel, austenite conditioning, austenite transformation, structure, retained austenite, tensile deformation, neutron diffraction, load partitioning, mechanical properties.

Fractionation of heavy metals in runoff and discharge of a stormwater management system and its implications for treatment

A stormwater management system utilizing the mechanisms of sedimentation and filtration/infiltration was developed and constructed for the immobilization of suspended solids and heavy metal constituents (Fe, Zn, Pb, Cr, Cu, Cd, Ni) in runoff. Monitoring took place between May 2010 and November 2012 on a total of 24 storm events. This research on the fractionation of heavy metals in runoff and discharge of a stormwater system provided insight on the actual efficiency of the system and determined the implications for treatment of the particulate-bound and dissolved heavy metals in runoff. Results revealed that the partitioning of heavy metal load in runoff in either dissolved or particulate-bound were influenced by flow rate and total suspended solids load, and evident in high-intensity storm (rainfall-runoff event). On the other hand, the partitioning of heavy metal load discharge from the stormwater system was more apparent during the early period of discharge having higher variability in dissolved than particulate-bound heavy metal. Findings revealed that fractionation of heavy metals played an important role in the performance of the stormwater system; thus, must be considered in designing stormwater systems. For the stormwater system to be effective, it is recommended to design the system treating not only the early period of a storm (first flush criteria) rather until the peak part of the hydrograph (high flow rate where partitioning was greatest) from a load basis.

Declarative platform for high-performance network traffic analytics

This paper presents Scalanytics, a declarative platform that supports high-performance application layer analysis of network traffic. Scalanytics uses (1) stateful network packet processing techniques for extracting application layer data from network packets, (2) a declarative rule-based language called Analog for compactly specifying analysis pipelines from reusable modules, and (3) a task-stealing architecture for processing network packets at high throughput within these pipelines, by leveraging multi-core processing capabilities in a load-balanced manner without the need for explicit performance profiling. In a cluster of machines, Scalanytics further improves throughput through the use of a consistent-hashing based load partitioning strategy. Our evaluation on a 16-core machine demonstrate that Scalanytics achieves up to 11.4 $$\times $$ × improvement in throughput compared with the best uniprocessor implementation. Moreover, Scalanytics outperforms the Bro intrusion detection system by an order of magnitude when used for analyzing SMTP traffic. We further observed increased throughput when running Scalanytics pipelines across multiple machines.

Partitioning of knee joint internal forces in gait is dictated by the knee adduction angle and not by the knee adduction moment

Medial knee osteoarthritis is a debilitating disease. Surgical and conservative interventions are performed to manage its progression via reduction of load on the medial compartment or equivalently its surrogate measure, the external adduction moment. However, some studies have questioned a correlation between the medial load and adduction moment. Using a musculoskeletal model of the lower extremity driven by kinematics–kinetics of asymptomatic subjects at gait midstance, we aim here to quantify the relative effects of changes in the knee adduction angle versus changes in the adduction moment on the joint response and medial/lateral load partitioning. The reference adduction rotation of 1.6° is altered by ±1.5° to 3.1° and 0.1° or the knee reference adduction moment of 17Nm is varied by ±50% to 25.5Nm and 8.5Nm. Quadriceps, hamstrings and tibiofemoral contact forces substantially increased as adduction angle dropped and diminished as it increased. The medial/lateral ratio of contact forces slightly altered by changes in the adduction moment but a larger adduction rotation hugely increased this ratio from 8.8 to a 90 while in contrast a smaller adduction rotation yielded a more uniform distribution. If the aim in an intervention is to diminish the medial contact force and medial/lateral load ratio, a drop of 1.5° in adduction angle is much more effective (causing respectively 12% and 80% decreases) than a reduction of 50% in the adduction moment (causing respectively 4% and 13% decreases). Substantial role of changes in adduction angle is due to the associated alterations in joint nonlinear passive resistance. These findings explain the poor correlation between knee adduction moment and tibiofemoral compartment loading during gait suggesting that the internal load partitioning is dictated by the joint adduction angle.

Enhancing Intradomain Scalability of IMS-Based Services

IP multimedia subsystem (IMS) and IMS-based services are increasingly providing interoperable session control and mobility for next-generation all-IP networks. However, clear design guidelines and techniques for the support of scalable IMS-based deployment, especially for data-intensive services such as mobility management, presence, and instant messaging, are still missing. That could block or at least relevantly slow down IMS acceptance by network operators and application providers. To address these challenges, this paper thoroughly analyzes IMS scalability with special attention to intradomain deployment issues. Then, it proposes a novel solution with three core original contributions toward intradomain scalability: 1) data-centric dissemination of session state with limited overhead; 2) service-aware routing for fast intradomain load balancing; 3) service-aware load monitoring and component de-/activation for long-term intradomain load partitioning at both service and infrastructure levels. The reported experimental results point out that our solution can significantly increase intradomain scalability with very limited costs.

In Situ Characterization of Twin Nucleation in Pure Ti Using 3D-XRD

A small tensile specimen of grade 1 commercially pure titanium was deformed to a few percent strain with concurrent synchrotron X-ray diffraction measurements to identify subsurface {10\( \bar{1} \)2} twin nucleation events. This sample was from the same piece of material in which a prior study showed that twin nucleation stimulated by slip transfer across a grain boundary accounted for many instances of twin nucleation. The sample had a strong c-axis texture of about eight times random aligned with the tensile axis. After ~1.5 pct tensile strain, three twin nucleation events were observed in grains where the c-axis was nearly parallel to the tensile direction. Far-field 3-D X-ray diffraction data were analyzed to obtain the positional center of mass, the average lattice strain, and stress tensors in each grain and twin. In one case where the parent grain was mostly surrounded by hard grain orientations, the twin system with the highest resolved shear stress (RSS) among the six {10\( \bar{1} \)2} twin variants was activated and the stress in the parent grain decreased after twin nucleation. In two other parent grains with a majority of softer neighboring grain orientations, the observed twins did not occur on the twin system with the highest RSS. Their nucleation could be geometrically attributed to slip transfer from neighboring grains with geometrically favorable 〈a〉 basal slip systems, and the stress in the parent grain increased after twin nucleation. In all three twin events, the stress in the twin was 10 to 30 pct lower than the stress in the parent grain, indicating load partitioning between the hard-oriented parent grain and the soft-oriented twin.

The mechanical stability of retained austenite in low-alloyed TRIP steel under shear loading

The microstructure evolution during shear loading of a low-alloyed TRIP steel with different amounts of the metastable austenite phase and its equivalent DP grade has been studied by in-situ high-energy X-ray diffraction. A detailed powder diffraction analysis has been performed to probe the austenite-to-martensite transformation by characterizing simultaneously the evolution of the austenite phase fraction and its carbon concentration, the load partitioning between the austenite and the ferritic matrix and the texture evolution of the constituent phases. Our results show that for shear deformation the TRIP effect extends over a significantly wider deformation range than for simple uniaxial loading. A clear increase in average carbon content during the mechanically-induced transformation indicates that austenite grains with a low carbon concentration are least stable during shear loading. The observed texture evolution indicates that under shear loading the orientation dependence of the austenite stability is relatively weak, while it has previously been found that under tensile load the {110}〈001〉 component transforms preferentially. The mechanical stability of retained austenite in TRIP steel is found to be a complex interplay between the interstitial carbon concentration in the austenite, the grain orientation and the load partitioning.